1. Field of the Invention
In general, this invention pertains to friction stir welds. Specifically, this invention pertains to an apparatus for making a friction stir weld around the circumference of a cylindrical work piece.
2. Background Information
Friction stir welding is a relatively new welding technique for joining like materials together. The friction stir technique uses a frictional heat source to plasticize adjoining sections of the same material. Once plasticized, the frictional heat source is removed and the sections join together. A rapidly spinning probe, which must be capable of sustaining the requisite plasticized temperatures, is commonly used as the frictional heat source. The spinning probe also facilitates mixing of the material in the plasticized region. A more complete description of friction stir welding can be found in U.S. Pat. No. 5,460,317.
Like most new techniques, friction stir welding is not without its challenges. For example, significant forces are necessary for a spinning probe to penetrate and remain within the sections of a work piece that are to be joined. As a result, the weld joint must be properly supported on the back side in order to make the friction stir weld possible or prevent unwanted damage to the work piece. Providing back-side weld support can be nothing short of difficult with particular work piece geometries.